Radial thrust bearings

[CDK]

Originally Posted by owene

Yes, although if I'm going to the effort of machining one up, I may as well do three (one spare)..... Good food for thought.

No, just the one at the rear. You press the two halves in the groove, slide the cupped washer over them and install the bearings. Doing the same at the front is possible only when the cupped washer comes last and all axial play is eliminated or at least reduced to a gap small enough so the collars cannot slide out once the bearings have run in.
And if you ever need the 3rd set, you have been in big trouble!

[gonzo]

All motors are on rubber mounts. How is this sophisticated or different? You just put a coupler, get rid of any spline unless it is locked, and bolt them together.

[marshmat]

Gonzo- For whatever reason, Owen's drivetrain has universal joints in it. Possibly because the geometry wasn't favourable for having just a straight shaft to the engine, or perhaps it's so that the engine can be on soft vibration-damping mounts (the reason that Dashew yachts and many other high-end craft use CV joints). Since the universal joints won't transmit axial loads directly to the transmission, an additional thrust bearing is needed.

[owene]

Gonzo, I guess that you haven't read my first posting. Not all motors are on rubber mounts but mine is. If I put it on fixed mounts with a direct coupling to the shaft, the motor would be tilted up at 18 degrees to match the shaft - somehow I doubt the Cummins warranty would be worth more than a roll of dunny paper. Also, if I do away with the rubber mounts, the boat will sound like a drumming machine with all of those engine noises. Marshmat's comment above is exactly correct.

[gonzo]

I haven´t seen an engine that is not on rubber mounts in years. Old wooden boats had hard mounts, but the hulls are flexible and absorb vibration. 18 degrees is a lot. They make drop angle transmissions for that application. It would be much cheaper than engineering a thrust bearing and mounts for it. U joints should be able to take the thrust if they are sized properly. The small length difference will be taken by the shaft sliding on the cutlass bearing like on every other installation.

[CDK]

No Gonzo, you're wrong. Rubber engine mounts that have to cope with axial loads are made to offer some transverse movement, but in the axial direction they are stone hard (width/length 1:4 or more) and transmit a lot of vibration.
A far superior way is to use soft mounts, double universal joints and a thrust bearing.

And of course the angled joints cannot take any axial force, no matter how large they are. That is a basic engineering rule.

[gonzo]

I know I am not wrong. The mounts are a bolt surrounded by rubber.

[CDK]

As always, there are cheap ones and good ones.

The one in your picture is stone hard in any direction because the rubber has nowhere to go.

[gonzo]

Come on CDK I show you were wrong and now you're being petty. The upper one you show is a Yanmar type. They move in all directions until the metal stops it. The lower one is the same. The photos I posted are the factory mounts for Mercruiser and VolvoPenta. They are not rock solid, that is BS. The rubber allows some movement. If you want to discuss a point do it with the truth.

[mydauphin]

I am on your same mission, lets talk, I have other parts of system, email me at mydauphin@gmail.com Perhaps we can build 6 and save some money.

[CDK]

Originally Posted by gonzo

Come on CDK I show you were wrong and now you're being petty. The upper one you show is a Yanmar type. They move in all directions until the metal stops it. The lower one is the same. The photos I posted are the factory mounts for Mercruiser and VolvoPenta. They are not rock solid, that is BS. The rubber allows some movement. If you want to discuss a point do it with the truth.

The pictures I posted came from Marine24.com and are no standard issue for any engine, although the diesel engines I have seen installed in sailing boats and cruisers (also Volvo) without exception were this type. They are available in 50 and 60 shore and allow a lot of movement sideways, but axially it is limited to a few mm's only. The geometry is approx. 1:4.

The one from your picture I've seen under large industrial electric motors, under small diesel generators and a few times in fishing boats. I've had 5 Mercruisers and one OMC, none equipped with such feet.

The diesel engines in my boat stand on cylindrical feet of a different design. They cannot take any axial force at all, but they don't have to because the thrust bearings are incorporated in the oil filled stern tubes.

[gonzo]

A few milimiters of fore an aft play is not rock solid. The mount I posted is from the Mercruiser catalog.